DESIGN AND EXPERIMENT ON PROBE-FED SLOTTED MICROSTRIP ANTENNA
In this paper, a novel design of microstrip antenna for wireless communication applications is presented. Theantenna employs a co-axial probe fed, slots with air filled substrate medium that is located over a ground plane for betterradiation performance. Parameters of the antenna includes, a measured gain of 4.7 dB, bandwidth of 290 MHz,miniaturization of 27 %, good radiation pattern with a return loss of -22.07 dB. This low cost microstrip design allows forsimple integration with surface mount components. The antenna is designed for S-band applications such as WiMaxoperating in the frequency range of 3.3 – 3.6 GHz, fixed satellite services, maritime mobile services etc covering 2 - 4 GHzfrequency range. Details of the design procedure and results of return loss (RL), bandwidth, radiation patterns are given
Content
International Journal of Electrical and Electronics Engineering Research (IJEEER) ISSN 2250-155X Vol. 2 Issue 4 Dec - 2012 21-24 © TJPRC Pvt. Ltd.,
DESIGN AND EXPERIMENT ON PROBE-FED SLOTTED MICROSTRIP ANTENNA
1 1, 2, 3
P. A. AMBRESH, 2P. M. HADALGI & 3P. V. HUNAGUND
Department of P.G. Studies & Research in Applied Electronics, Gulbarga University, Gulbarga-585106, India
ABSTRACT
In this paper, a novel design of microstrip antenna for wireless communication applications is presented. The antenna employs a co-axial probe fed, slots with air filled substrate medium that is located over a ground plane for better radiation performance. Parameters of the antenna includes, a measured gain of 4.7 dB, bandwidth of 290 MHz, miniaturization of 27 %, good radiation pattern with a return loss of -22.07 dB. This low cost microstrip design allows for simple integration with surface mount components. The antenna is designed for S-band applications such as WiMax operating in the frequency range of 3.3 – 3.6 GHz, fixed satellite services, maritime mobile services etc covering 2 - 4 GHz frequency range. Details of the design procedure and results of return loss (RL), bandwidth, radiation patterns are given.
KEY WORDS: Double Slots; Impedance Bandwidth; Miniaturize; Radiation Pattern; VNA; Wimax INTRODUCTION
A miniature size antenna is finding increasing usage in various wireless communication applications specifically in low microwave frequency range i.e., in S-band frequency allocation. Hence, antenna with miniature structure is required for practical use. Many methods for achieving miniaturization of the antenna have been observed through simulation and experiment [1 – 6]. It is known that, the resonant frequency of a microstrip antenna is inversely proportional to dielectric constant. It is also possible to reduce the resonant frequency by using a substrate with high dielectric constant [7]. Here, a novel technique is proposed, where two slots are introduced on the patch with air dielectric medium for a rectangular microstrip antenna and also by the use of substrate with high dielectric constant. These slots appear as discontinuity to the microstrip transmission line and provide a transverse component of current, which generates a longitudinal component of the magnetic field and can be modeled as series inductance [8]. Hence the electrical length of the patch increases, thus lowering the resonant frequency, that is, the antenna size is reduced (compact) for a fixed frequency operation. Thus experimental results show a reduction in resonant frequency.
DESIGN & EXPERIMENTAL RESULTS
Fig. 1 shows the slotted microstrip antenna (SMA) with length L = 17.76 mm, width W = 23.28 mm (L<W), and substrate with dielectric constant Єr = 4.4 and thickness h = 1.6 mm is calculated and the patch design was carried out using computer software AutoCAD-2008. The designed frequency of the patch antenna is 3.80 GHz. Here, coaxial probe feeding is used and the feed position has been chosen on the line of symmetry and at a distance Xf = L/2[Єreff(sqrt(L))]1/2, as given by M. Kara [9]. The copper plate is used as ground plane with dimension Lg x Wg = 40 x 40 mm having thickness 0.16 cm. When a pair of slots are etched on the copper patch surface and is finally structured as slotted microstrip antenna (SMA) with its optimized slot dimensions as L1 = 19.14 mm, L2 = 1.3 mm, W1 = 4.86 mm, W2 = 6.51 mm, S1 = 6.17 mm, S2 = 2.01 mm, S3 = 8.04 mm, S4 = 9.15 mm, S5 = 2.68 mm makes the antenna resonate at a lower frequency of 3.53 GHz as shown in Fig. 2. This resonant frequency covers range of 3.40 GHz to 3.69 GHz which is suitable for practical S- band
22
P. A. Ambresh, P. M. Hadalgi & P. V. Hunagund
wireless applications. An impedance bandwidth of 290 MHz (8.90 %) is obtained at resonant frequency with a moderate gain of 4.6 dB. It can be observed that the resonant frequency of the SMA is reduced compared to the designed frequency hence, a compactness of 26 % is achieved. The radiation pattern of SMA is measured and it is found that the pattern remains broadband, similar to that of a simple microstrip antenna, with almost omni-directional radiation pattern as shown in Fig. 3.
Figure 1: Slotted Microstrip Antenna (SMA)
Bandwidth (BW1) = 290 MHz
Return loss curve
Figure 2: Return Loss (RL) Characteristics Versus Frequency
90 0 -2 -4 -6 -8 -10 180 -10 -8 -6 -4 -2 0 240 270 300 210 Co-polar Cross polar 330 0 150 30 120 60
Figure 3: Measured Radiation Pattern at 3.53 GHz
Design and Experiment on Probe-Fed Slotted Microstrip Antenna
23
Fig. 4 (a) shows the measured input impedance loci using Smith chart justifying that the proposed design offered impedance of 48.49 + j11.68 almost matching the impedance (of the feed and antenna) in the operating band and the
measured VSWR is found to be 1.22 which is less than 1.5 signifying less reflected power throughout the operating band as depicted in Fig. 4 (b).
(a)
(b)
Figure 4: (a) Smith Chart Characteristics and (b) Measured VSWR
CONCLUSIONS
In this paper, a novel type of probe fed microstrip antenna is discussed & presented. Advantages of such new antenna design include ease of construction, relatively low cost and good radio frequency performance. Specifically, the antenna produced a well formed omnidirectional radiation pattern with moderate gain (4.7 dB), and good impedance match covering 3.40 GHz to 3.69 GHz band.
ACKNOWLEDGMENTS
Authors convey thanks to the authorities of Department of Science and Technology (DST), Government of India, New Delhi, for sanctioning Vector Network Analyzer to the Department of Applied Electronics, Gulbarga University, Gulbarga under FIST Project and also providing financial assistance to Mr.Ambresh P Ambalgi under Rajiv Gandhi National fellowship [No.F.14-2(SC)/2009(SA-III) dated 18 November 2010] scheme by University Grants Commission (UGC), New Delhi.
REFERENCES
1. Sanad. M., (1994) Effect of shorting posts on short circuit microstrip antennas. IEEE Trans Antennas Propag. 42,794–797. 2. Kuga. N., & Arai.H. (1996) Circular patch antennas miniaturized by shorting posts. Electron Commun. Jpn, 79, 51–58. 3. 4. Wong. K.L., & Pan. S.S. (1997) Compact Triangular microstrip antenna. Electron Lett., 33, 433–434. Desclos, L. (2000) Size reduction of patch by means of slot insertion. Microwave and Optical Technology Letters, 25, 111–113. 5. Hong. J.S., & Lancaster. M.J., (1994) Capacitively loaded microstrip loop resonator. Electron Lett, 30, 1494– 1495.
24
P. A. Ambresh, P. M. Hadalgi & P. V. Hunagund
6.
Shackelford, A.K., Lee, K.-F., & Luk, K.M., (2003) Design of small-size wide-bandwidth microstrip-patch antennas. IEEE Trans Microwave Theory Tech., 45, 75–83.
7.
Lo, T.K., Ho, C.o., Hwang, Y., Lam, E.K.W., & Lee, B., (1997) Miniature aperture-coupled microstrip antenna of very high permittivity. Electron Lett, 33, 9-10.
8.
Hoefer, W.J.R., (1977) Equivalent series inductivity of a narrow transverse slit in microstrip. IEEE Trans Microwave Theory Tech. 25, 822– 824.
9.
Kara, M., (1996) Formulas for the computation of physical properties of rectangular microstrip antenna elements with various substrate thicknesses. Microwave and Optical Technology Letters, 12, 268–272.
DESIGN AND EXPERIMENT ON PROBE-FED SLOTTED MICROSTRIP ANTENNA
1 1, 2, 3
P. A. AMBRESH, 2P. M. HADALGI & 3P. V. HUNAGUND
Department of P.G. Studies & Research in Applied Electronics, Gulbarga University, Gulbarga-585106, India
ABSTRACT
In this paper, a novel design of microstrip antenna for wireless communication applications is presented. The antenna employs a co-axial probe fed, slots with air filled substrate medium that is located over a ground plane for better radiation performance. Parameters of the antenna includes, a measured gain of 4.7 dB, bandwidth of 290 MHz, miniaturization of 27 %, good radiation pattern with a return loss of -22.07 dB. This low cost microstrip design allows for simple integration with surface mount components. The antenna is designed for S-band applications such as WiMax operating in the frequency range of 3.3 – 3.6 GHz, fixed satellite services, maritime mobile services etc covering 2 - 4 GHz frequency range. Details of the design procedure and results of return loss (RL), bandwidth, radiation patterns are given.
KEY WORDS: Double Slots; Impedance Bandwidth; Miniaturize; Radiation Pattern; VNA; Wimax INTRODUCTION
A miniature size antenna is finding increasing usage in various wireless communication applications specifically in low microwave frequency range i.e., in S-band frequency allocation. Hence, antenna with miniature structure is required for practical use. Many methods for achieving miniaturization of the antenna have been observed through simulation and experiment [1 – 6]. It is known that, the resonant frequency of a microstrip antenna is inversely proportional to dielectric constant. It is also possible to reduce the resonant frequency by using a substrate with high dielectric constant [7]. Here, a novel technique is proposed, where two slots are introduced on the patch with air dielectric medium for a rectangular microstrip antenna and also by the use of substrate with high dielectric constant. These slots appear as discontinuity to the microstrip transmission line and provide a transverse component of current, which generates a longitudinal component of the magnetic field and can be modeled as series inductance [8]. Hence the electrical length of the patch increases, thus lowering the resonant frequency, that is, the antenna size is reduced (compact) for a fixed frequency operation. Thus experimental results show a reduction in resonant frequency.
DESIGN & EXPERIMENTAL RESULTS
Fig. 1 shows the slotted microstrip antenna (SMA) with length L = 17.76 mm, width W = 23.28 mm (L<W), and substrate with dielectric constant Єr = 4.4 and thickness h = 1.6 mm is calculated and the patch design was carried out using computer software AutoCAD-2008. The designed frequency of the patch antenna is 3.80 GHz. Here, coaxial probe feeding is used and the feed position has been chosen on the line of symmetry and at a distance Xf = L/2[Єreff(sqrt(L))]1/2, as given by M. Kara [9]. The copper plate is used as ground plane with dimension Lg x Wg = 40 x 40 mm having thickness 0.16 cm. When a pair of slots are etched on the copper patch surface and is finally structured as slotted microstrip antenna (SMA) with its optimized slot dimensions as L1 = 19.14 mm, L2 = 1.3 mm, W1 = 4.86 mm, W2 = 6.51 mm, S1 = 6.17 mm, S2 = 2.01 mm, S3 = 8.04 mm, S4 = 9.15 mm, S5 = 2.68 mm makes the antenna resonate at a lower frequency of 3.53 GHz as shown in Fig. 2. This resonant frequency covers range of 3.40 GHz to 3.69 GHz which is suitable for practical S- band
22
P. A. Ambresh, P. M. Hadalgi & P. V. Hunagund
wireless applications. An impedance bandwidth of 290 MHz (8.90 %) is obtained at resonant frequency with a moderate gain of 4.6 dB. It can be observed that the resonant frequency of the SMA is reduced compared to the designed frequency hence, a compactness of 26 % is achieved. The radiation pattern of SMA is measured and it is found that the pattern remains broadband, similar to that of a simple microstrip antenna, with almost omni-directional radiation pattern as shown in Fig. 3.
Figure 1: Slotted Microstrip Antenna (SMA)
Bandwidth (BW1) = 290 MHz
Return loss curve
Figure 2: Return Loss (RL) Characteristics Versus Frequency
90 0 -2 -4 -6 -8 -10 180 -10 -8 -6 -4 -2 0 240 270 300 210 Co-polar Cross polar 330 0 150 30 120 60
Figure 3: Measured Radiation Pattern at 3.53 GHz
Design and Experiment on Probe-Fed Slotted Microstrip Antenna
23
Fig. 4 (a) shows the measured input impedance loci using Smith chart justifying that the proposed design offered impedance of 48.49 + j11.68 almost matching the impedance (of the feed and antenna) in the operating band and the
measured VSWR is found to be 1.22 which is less than 1.5 signifying less reflected power throughout the operating band as depicted in Fig. 4 (b).
(a)
(b)
Figure 4: (a) Smith Chart Characteristics and (b) Measured VSWR
CONCLUSIONS
In this paper, a novel type of probe fed microstrip antenna is discussed & presented. Advantages of such new antenna design include ease of construction, relatively low cost and good radio frequency performance. Specifically, the antenna produced a well formed omnidirectional radiation pattern with moderate gain (4.7 dB), and good impedance match covering 3.40 GHz to 3.69 GHz band.
ACKNOWLEDGMENTS
Authors convey thanks to the authorities of Department of Science and Technology (DST), Government of India, New Delhi, for sanctioning Vector Network Analyzer to the Department of Applied Electronics, Gulbarga University, Gulbarga under FIST Project and also providing financial assistance to Mr.Ambresh P Ambalgi under Rajiv Gandhi National fellowship [No.F.14-2(SC)/2009(SA-III) dated 18 November 2010] scheme by University Grants Commission (UGC), New Delhi.
REFERENCES
1. Sanad. M., (1994) Effect of shorting posts on short circuit microstrip antennas. IEEE Trans Antennas Propag. 42,794–797. 2. Kuga. N., & Arai.H. (1996) Circular patch antennas miniaturized by shorting posts. Electron Commun. Jpn, 79, 51–58. 3. 4. Wong. K.L., & Pan. S.S. (1997) Compact Triangular microstrip antenna. Electron Lett., 33, 433–434. Desclos, L. (2000) Size reduction of patch by means of slot insertion. Microwave and Optical Technology Letters, 25, 111–113. 5. Hong. J.S., & Lancaster. M.J., (1994) Capacitively loaded microstrip loop resonator. Electron Lett, 30, 1494– 1495.
24
P. A. Ambresh, P. M. Hadalgi & P. V. Hunagund
6.
Shackelford, A.K., Lee, K.-F., & Luk, K.M., (2003) Design of small-size wide-bandwidth microstrip-patch antennas. IEEE Trans Microwave Theory Tech., 45, 75–83.
7.
Lo, T.K., Ho, C.o., Hwang, Y., Lam, E.K.W., & Lee, B., (1997) Miniature aperture-coupled microstrip antenna of very high permittivity. Electron Lett, 33, 9-10.
8.
Hoefer, W.J.R., (1977) Equivalent series inductivity of a narrow transverse slit in microstrip. IEEE Trans Microwave Theory Tech. 25, 822– 824.
9.
Kara, M., (1996) Formulas for the computation of physical properties of rectangular microstrip antenna elements with various substrate thicknesses. Microwave and Optical Technology Letters, 12, 268–272.
